DTV transmitter and method of coding main and enhanced data in DTV transmitter

ABSTRACT

A DTV transmitter includes a pre-processor pre-processing enhanced data, a data formatter generating enhanced data packets including the pre-processed data and inserting known data place holders to the data packets, and a multiplexer multiplexing the enhanced data packets with main data packets. It further includes an RS encoder which RS-codes the multiplexed data packets, and a data interleaves which interleaves the RS-coded data packets. The RS encoder adds systematic RS parity data to each main data packet and adds non-systematic RS parity place holders to each enhanced data packet. The RS encoder adds the RS parity place holders such that the RS parity place holders are placed after the enhanced data within each interleaved enhanced data packet.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/564,821 filed on Nov. 29, 2006 now U.S. Pat. No. 7,783,960, whichclaims the benefit of and right of priority to the Korean PatentApplication No. 10-2005-0116042, filed on Nov. 30, 2005, and U.S.Provisional Application No. 60/825,267, filed on Sep. 11, 2006, thecontents of which are hereby incorporated by reference herein in theirentireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a digital telecommunications system,and more particularly, to a digital television (DTV) transmitter and amethod of coding main and enhanced data in a DTV transmitter.

2. Discussion of the Related Art

The Terrestrial-Vestigial Side Band (T-VSB) transmission mode, which isadopted as the standard for digital broadcasting in North America andthe Republic of Korea, is a system that has been developed for thetransmission of MPEG video/audio data. However, presently, thetechnology for processing digital signals is being developed at a vastrate, and, as a larger number of the population uses the Internet,digital electric appliances, computers, and the Internet are beingintegrated. Therefore, in order to meet with the various requirements ofthe users, a system that can add video/audio data through a digitaltelevision channel so as to transmit diverse supplemental informationneeds to be developed.

Some users may assume that supplemental data broadcasting would beapplied by using a PC card or a portable device having a simple in-doorantenna attached thereto. However, when used indoors, the intensity ofthe signals may decrease due to a blockage caused by the walls ordisturbance caused by approaching or proximate mobile objects.Accordingly, the quality of the received digital signals may bedeteriorated due to a ghost effect and noise caused by reflected waves.However, unlike the general video/audio data, when transmitting thesupplemental data, the data that is to be transmitted should have a lowerror ratio. More specifically, in case of the video/audio data, errorsthat are not perceived or acknowledged through the eyes or ears of theuser can be ignored, since they do not cause any or much trouble.Conversely, in case of the supplemental data (e.g., program executionfile, stock information, etc.), an error even in a single bit may causea serious problem. Therefore, a system highly resistant to ghost effectsand noise is required to be developed.

The supplemental data are generally transmitted by a time-divisionmethod through the same channel as the MPEG video/audio data. However,with the advent of digital broadcasting, ATSC VSB digital televisionreceivers that receive only MPEG video/audio data are already suppliedto the market. Therefore, the supplemental data that are transmittedthrough the same channel as the MPEG video/audio data should notinfluence the conventional ATSC VSB receivers that are provided in themarket. In other words, this may be defined as ATSC VSB compatibility,and the supplemental data broadcast system should be compatible with theATSC VSB system. Herein, the supplemental data may also be referred toas enhanced data or E-VSB data. Furthermore, in a poor channelenvironment, the receiving performance of the conventional ATSC VSBreceiving system may be deteriorated. More specifically, resistance tochanges in channels and noise is more highly required when usingportable and/or mobile receivers.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a digital television(DTV) transmitter and a method of coding main and enhanced data fordata, transmission in a DTV transmitter that substantially obviate oneor more problems due to limitations and disadvantages of the relatedart.

An object of the present invention is to provide a digital televisionsystem that is suitable for transmitting supplemental data and that ishighly resistant to noise.

Another object of the present invention is to provide a digitalbroadcasting system and method of processing data that can insert knowndata in a specific domain of the supplemental data and transmitting thedata to a DTV transmitter/receiver, thereby enhancing the receivingperformance of the digital television system.

A further object of the present invention is to provide a digitalbroadcasting system and processing method for efficiently inserting andtransmitting the known data.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, adigital television (DTV) receiver includes a pre-processor, a dataformatter, a multiplexer, an RS encoder, and a data interleaver. Thepre-processor may pre-process the enhanced data by coding the enhanceddata for forward error correction (FEC) and expand the FEC-codedenhanced data. The data formatter may generate enhanced data packetsincluding the pre-processed enhanced data and insert known data placeholders to at least one of the enhanced data packets. The multiplexermay multiplex the enhanced data packets with main data packets includingthe main data. The RS encoder may RS-code the multiplexed main andenhanced data packets, the RS encoder adds systematic RS parity data toeach main data packet and adds non-systematic RS parity place holders toeach enhanced data packet. The data interleaver may interleave theRS-coded main and enhanced data packets, wherein the non-systematic RSparity place holders are placed after the enhanced data within eachinterleaved enhanced data packet.

The data interleaver may replace the RS parity place holders included ineach interleaved enhanced data packet with non-systematic RS paritydata.

The DTV transmitter may further include a known data, a byte-symbolconverter, a symbol processor, and a trellis encoder. The known datagenerator may generate known data symbols. The byte-symbol converter mayconvert the interleaved data packets into corresponding symbols. Thesymbol processor may process the symbols, the symbol processor encodessymbols corresponding to the enhanced data and replaces symbolscorresponding to the known data place holders with the known datasymbols. The trellis encoder may trellis-encode the symbols processed bythe symbol processor, the trellis encoder is initialized when thesymbols outputted from the symbol processor are symbols representing abeginning of a known data sequence.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiments of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates a block view of a digital broadcast transmittingsystem according to the present invention;

FIG. 2A illustrates a block view of an E-VSB symbol processor accordingto an embodiment of the present invention;

FIG. 2B illustrates a block view of an E-VSB symbol processor accordingto another embodiment of the present invention;

FIG. 3A to FIG. 3C illustrate examples of expanding one enhanced databyte to two bytes according to the present invention;

FIG. 4A to FIG. 4C illustrate examples of expanding one enhanced databyte to four bytes according to the present invention;

FIG. 5 illustrates a block view of a pre-coder bypass unit according toan embodiment of the present invention;

FIG. 6A illustrates a block view of a trellis encoder according to anembodiment of the present invention;

FIG. 6B illustrates an example of an input symbol for initializing amemory of the trellis encoder according to the present invention; and

FIG. 7 illustrates a block view showing a general structure of a digitalbroadcast receiving system according to an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

In addition, although the terms used in the present invention areselected from generally known and used terms, some of the termsmentioned in the description of the present invention have been selectedby the applicant at his or her discretion, the detailed meanings ofwhich are described in relevant parts of the description herein.Furthermore, it is required that the present invention is understood,not simply by the actual terms used but by the meaning of each termlying within.

In the present invention, the enhanced data may either consist of dataincluding information such as program execution files, stockinformation, weather information, and so on, or consist of video/audiodata. Additionally, the known data refer to data already known basedupon a pre-determined agreement between the transmitter and thereceiver. Furthermore, the main data consist of data that can bereceived from the conventional receiving system, wherein the main datainclude video/audio data.

The present invention relates to inserting known data known by thetransmitter/receiver in a specific position of an enhanced data packetand transmitting the processed data packet, thereby enhancing thereceiving performance of the receiving system. Most particularly, thepresent invention relates to multiplexing the enhanced data includingthe known data and the main data in packet units, thereby performingadditional encoding of only the enhanced data when encoding themultiplexed data in a symbol domain. Finally, the present inventionenables a long known data sequence to be inserted consecutively, therebyenhancing the degree of freedom for deciding the inserting position ofthe known data sequence.

FIG. 1 illustrates a block view of a digital broadcast transmittingsystem according to the present invention. The digital broadcasttransmitting system includes an E-VSB pre-processor 101, an E-VSB packetformatter 102, a packet multiplexer 103, a data randomizer 104, ascheduler 105, a Reed-Solomon (RS) encoder/non-systematic Reed-Solomon(RS) parity place holder inserter 106, a data interleaver 107, abyte-symbol converter 108, an E-VSB symbol processor 109, a known datagenerator 110, a symbol-byte converter 111, a non-systematic RS encoder112, a trellis encoder 113, a frame multiplexer 114, and a transmitter120.

In the present invention having the above-described structure, a maindata packet is outputted to the packet multiplexer 103, and enhanceddata are outputted to the E-VSB pre-processor 101. The E-VSBpre-processor 101 pre-processes the enhanced data, such as encodingadditional error correction, interleaving, and inserting null data, andthen outputs the pre-processed enhanced data to the E-VSB packetformatter 102.

Based upon the control of the scheduler 105, the E-VSB packet formatter102 multiplexes the pre-processed enhanced data and the known data placeholder having the null data inserted therein, thereby configuring agroup. Herein, the known data place holder ensures in advance theposition (or place) in which the known data are to be inserted in alater process. The data within the group are then divided into 184-byteunit enhanced data packets, and a 4-byte MPEG header is added to thebeginning of the enhanced data packet, thereby outputting a 188-byteenhanced data packet (i.e., a MPEG compatibility packet). Herein, theMPEG header is configured of a 1-byte MPEG synchronization byte (0x47)and a 3-byte packet identification (Pin). In addition, one enhanced datapacket group includes a plurality of consecutive enhanced data packets.

The output of the E-VSB packet formatter 102 is inputted to the packetmultiplexer 103. The packet multiplexer 103 time-division multiplexesthe main data packet and the enhanced data packet group in transportstream (TS) packet units and outputs the multiplexed TS packet inaccordance with the control of the scheduler 105. More specifically, thescheduler 105 generates and outputs a control signal so that the packetformatter 102 can multiplex the main data packet and the enhanced datapacket group. Accordingly, the packet multiplexer 103 receives thecontrol signal, thereby multiplexing and outputting the main data packetand the enhanced data packet group to TS packet units.

The output data of the packet multiplexer 103 are inputted to the datarandomizer 104. The data randomizer 104 discards (or deletes) the MPEGsynchronization byte and randomizes the remaining 187 bytes by using apseudo-random byte, which is generated from inside the data randomizer104. Thereafter, the randomized data are outputted to the Reed-Solomon(RS) encoder/non-systematic RS parity place holder inserter 106. The RSencoder/non-systematic RS parity place holder inserter 106 processes therandomized data with either a systematic RS-coding process or anon-systematic RS parity place holder insertion process. Morespecifically, when the 187-byte packet that is outputted from the datarandomizer 104 corresponds to the main data packet, RSencoder/non-systematic RS parity place holder inserter 106 performs thesame systematic RS-coding as the conventional ATSC VSB system, therebyadding a 20-byte parity byte at the end of the 187-byte data andoutputting a 207-byte packet. The rule (or principle) of inserting the20 null data bytes within the enhanced data packet will be described ina later process. Herein, the null byte may be given an arbitrary value,and such null byte value may be substituted with the parity valuecalculated by the non-systematic RS encoder 112 in a later process.Accordingly, the role of the null byte is to ensure the parity byteposition (or place) of a non-systematic RS code.

The non-systematic RS code is used for the enhanced data packet for thefollowing reason. When the value of the enhanced data is changed by theE-VSB symbol processor 109, which will be described in detail in a laterprocess, the RS parity should be recalculated. And so, the parity bytesshould be outputted from the data interleaver 107 output terminal laterthan the data bytes. For example, when K number of data bytes arereceived and P number of parity bytes are added thereto so as to beRS-coded, P number of arbitrary bytes among the total N(=K+P) number ofbytes may be used as the parity bytes.

The output of the RS encoder/non-systematic RS parity place holderinserter 106 is configured of a 207-byte packet. The order in which thebytes within the packet are outputted from the encoder/inserter 106 isdetermined in accordance with Equation 1 below.b=((52×p)+(s mod 52))mod 207, p=0, 1, . . . , 206  Equation 1Herein, s indicates a segment (or packet) number following the fieldsynchronization signal, and the value of s ranges from 0 to 311. Also, bindicates a byte position within the segment (or packet), and the valueof b ranges from 0 to 206. More specifically, s and b respectivelyrepresents each position of the segment (or packet) and the byteposition both being inputted to the data interleaver 107. Furthermore,52 indicates an invariable number pre-decided by the data interleaver107. And, finally, mod signifies a modulo operation.

Generally, in the ATSC VSB system, one transport packet is interleavedby the data interleaver, thereby being dispersed and outputted by aplurality of data segments. However, since one 207-byte packet has thedata size equal to that of one data segment, the packet may also be usedas a segment prior to the interleaving process. Therefore, when thevalues 0 to 205 are respectively substituted for p, the obtained value brepresents the position (or location) of the parity byte being inputtedinto the data interleaver 107. For example, in the above Equation 1, inthe first segment (wherein s=0), when the values p=0 to p=206 arerespectively substituted, the RS parity place holder is inputted intothe data interleaver 107 in a byte order of b=0, 52, 104, 156, 1, 53,105, 157, and so on.

Accordingly, when the input data correspond to the enhanced data packet,the RS encoder/non-systematic RS parity place holder inserter 106inserts a non-systematic RS parity place holder in a 20-byte place beingoutputted the latest from the output end of the data interleaver 107among the byte places excluding the MPEG header byte place and the knowndata byte place. More specifically, the 20 bytes that are to beoutputted the latest by the data interleaver 107, among the bytes in thedomain excluding the MPEG header byte and known data byte places, aredecided as the RS parity place holder. In other words, when viewed fromthe output end of the data interleaver 107, the known data place holdermay either be outputted later or be outputted earlier than the parityplace holder. The location of the parity byte being inputted into thedata interleaver 107 is determined in accordance with the Equation 1.And, as shown in Equation 1, the place of the non-systematic RS paritybyte of each segment (or packet) is different from one another.

The output data of the RS encoder/parity place holder inserter 106 areprovided to the data interleaver 107. Then, the data interleaver 107interleaves and outputs the received data. At this point, the datainterleaver 107 receives a RS parity byte that is newly calculated andoutputted by the non-systematic RS encoder 112 and, then, outputs thenewly received RS parity byte instead of the non-systematic RS parityplace holder. Each byte outputted from the data interleaves 107 isconverted into 4 symbols by the byte-symbol converter 108, which arethen inputted to the E-VSB symbol processor 109. Herein, one symbolconsists of 2 bits. Additionally, the known data generated (or created)from the known data generator 110 are also inputted to the E-VSB symbolprocessor 109. Herein, the known data consist of the known data symbolgenerated from the symbol domain. This is because the known data areused in the symbol domain of the receiving system. Also, in thetransmitting system, it is more efficient to create a known data symbolsequence having the characteristics desired (or required) by the symboldomain.

The E-VSB symbol processor 109 receives the data outputted from thebyte-symbol converter 108 and the known data symbol generated from theknown data generator 110, processes the received data with a pluralityof processing steps. Thereafter, the E-VSB symbol processor 109 outputsthe processed data to the trellis encoder 113. In other words, the E-VSBsymbol processor 109 receives the symbol configured of 2 bits andperforms a predetermined process. Then, the E-VSB symbol processor 109outputs processed symbol configured of 2 bits. In case of a main datasymbol, the E-VSB symbol processor 109 outputs the received symbolwithout any change in data. On the other hand, in case of an enhanceddata symbol, the received symbol is processed with a signal process thatcan provide additional coding gain when used in connection with thetrellis encoder 113. However, in the 207-byte enhanced data packet, the3-byte MPEG header and known data byte and the 20-byte RS parity byteare processed as the main data symbol. Therefore, the bytes are directlyoutputted without any change in the data value(s).

As described above, having the 3-byte MPEG header and known data byteand the 20-byte RS parity byte be directly outputted from the E-VSBsymbol processor 109 without any change in data value, and having thecorresponding bytes outputted from the output end of the datainterleaver later than the non-systematic RS parity byte, since only thepre-decided values are used, do not affect the non-systematic RS-codingprocess. Accordingly, the degree of freedom in choosing the insertionposition (or place) of the known data may be increased, thereby allowinga consecutive and long known data sequence to by obtained from thereceiver.

Meanwhile, when the input data inputted to the E-VSB symbol processor109 correspond to the known data place holder that is converted to asymbol by the byte-symbol converter 108, the E-VSB symbol processor 109uses the known data generated from the known data generator 110 insteadof the known data place holder. The E-VSB symbol processor 109 thengenerates a known data symbol at the beginning of the known datasequence so that the memory of the trellis encoder 113 is initialized toa pre-decided state. In order to do so, the memory value within thetrellis encoder 113 should be inputted to the E-VSB symbol processor109.

Further, the memory value of the trellis encoder 113 may also be used inan additional signaling process for the enhanced data symbol.Additionally, the trellis encoder 113 is initialized at the beginning ofthe known data sequence because a plurality of output sequences may begenerated depending upon the memory state of the trellis encoder 113even when the known data sequence is inputted to the trellis encoder113. Accordingly, the memory state of the trellis encoder 113 is firstinitialized to a pre-decided value and, then, when the known data areinputted, a desired known data output sequence may be obtained from theoutput of the trellis encoder 113.

In order to initialize the memory of the trellis encoder 113, twosymbols are required. And, since the VSB transmitting system includes 12trellis encoders, a total of input symbols are used for theinitialization process. More specifically, all of the 12 trellisencoders used in the ATSC VSB system are identical to one another.Therefore, 12 identical E-VSB symbol processors are also required in thestructure. The output symbol of the E-VSB symbol processor 109 isinputted to the trellis encoder 113 so as to be trellis-encoded.

The trellis encoder 113 pre-codes the data that are inputted as theupper bit among the output symbols of the E-VSB symbol processor 109,and trellis-encodes the data that are inputted as the lower bit.Thereafter, the pre-coded data and the trellis-encoded data areoutputted to the frame multiplexer 114. Meanwhile, the E-VSB symbolprocessor 109 receives the 2-bit symbol, processes the received symbolwith a plurality of process steps, and outputs the processed symbol.Therefore, the symbol should be converted back to bytes from thesymbol-byte converter 111 so that the non-systematic RS encoder 112 canrecalculate the RS parity from the output of the E-VSB symbol processor109. In other words, the input symbol is converted to byte units fromthe symbol-byte converter 111 and outputted to the non-systematic RSencoder 112. The non-systematic RS encoder 112 calculates the 20-byte RSparity for the data packet configured of 187 information bytes andoutputs the calculated RS parity to the data interleaver 107. The datainterleaver 107 receives the RS parity byte calculated and outputtedfrom the non-systematic RS encoder 112 and replaces the non-systematicplace holder that is not yet outputted with the received RS parity byte.

Herein, since the enhanced data symbol and the known data place holderare changed to different values by the E-VSB symbol processor 109, adecoding error occurs when performing a RS decoding process in theconventional ATSC VSB receiver. The non-systematic RS coding process isperformed in order to prevent such decoding error from occurring.Meanwhile, the non-systematic RS encoder 112 receives the output of theknown data generator 110 so that the symbol-byte converter 111 canreceive in advance the known data being outputted later than the RSparity byte.

The frame multiplexer 114 inserts 4 segment synchronization symbols ineach output symbol of the trellis encoder 113, thereby configuring adata segment having 832 data symbols. More specifically, one fieldsynchronization segment is inserted in each of the 312 data segments, soas to configure one data field, which is then outputted to thetransmitter 120. The transmitter 120 inserts a pilot signal in theoutput of the frame multiplexer 114, the output having a segmentsynchronization signal and a field synchronization signal insertedtherein. The transmitter 120 then VSB modulates the pilot signalinserted data and converts the VSB modulated data to an RF signal, whichis transmitted through the antenna. Accordingly, the transmitter 120includes a pilot inserter 121, a VSB modulator 122, and a RF-UPconverter 123. Furthermore, a pre-equalizer filter may be optionallyincluded.

FIG. 2A and FIG. 2B illustrate block views of an E-VSB symbol processoraccording to preferred embodiments of the present invention. Forsimplicity of the description, M represents the main data symbol, Tsignifies the known data symbol, and E represents the enhanced datasymbol. Herein, X2 corresponds to the upper bit among the 2 bits of theinput symbol, and X1 corresponds to the lower bit. At this point, if theMPEG header byte inserted to the enhanced data packet and the paritybyte inserted by the RS encoder are converted to symbols, the insertedbytes are processed as the main data symbol.

The E-VSB symbol processor of FIG. 2A includes first to fourthmultiplexers 201, 206, 204, and 207, a demultiplexer 202, a ½-codingrate encoder (hereinafter referred to as a “½-rate encoder”) 203, apre-coder bypass unit 205, and a trellis initialization controller 208.Referring to FIG. 2A, when the input symbol is one of a main data symbolM and an enhanced data symbol E, the first multiplexer 201 selects anupper bit X2 of a symbol outputted from the byte-symbol converter 108.Alternatively, when the input symbol is a known data symbol or a knowndata place holder symbol T, the first multiplexer 201 selects an upperbit X2 of a symbol outputted from the known data generator 110.Thereafter, the first multiplexer 201 outputs the selected upper bit X2to the demultiplexer 202.

Additionally, when the input symbol is one of a main data symbol M andan enhanced data symbol E, the second multiplexer 206 selects a lowerbit X1 of the symbol outputted from the byte-symbol converter 108. And,when the input symbol is a known data symbol or a known data placeholder symbol T, the second multiplexer 206 selects a lower bit X1 ofthe symbol outputted from the known data generator 110. Thereafter, thesecond multiplexer 206 outputs the selected lower bit X1 to the fourthmultiplexer 207. When the output bit outputted from the firstmultiplexer 201 is one of the upper bit of the main data symbol and theupper bit of the known data symbol, the demultiplexer 202 outputs theoutput bit to the third multiplexer 204. Alternatively, when the outputbit is the upper bit of the enhanced data symbol, the demultiplexer 202outputs the output bit to the ½-coding rate encoder (hereinafterreferred to as “½-rate encoder”) 203.

The ½-rate encoder 203 operates only on the enhanced data symbol,thereby coding the upper bit of the enhanced data symbol at a ½ codingrate and outputting two bits. At this point, among the output bits, oneis outputted to the pre-coder bypass unit 205 through the thirdmultiplexer 204, and the other is outputted to the fourth multiplexer207. When the input symbol is one of the main data symbol M and theknown data symbol T, the third multiplexer 204 selects the output of thedemultiplexer 202. And, when the input symbol is the enhanced datasymbol 2, the third multiplexer 204 selects one output bit of the ½-rateencoder 203 and outputs the selected bit to the pre-coder bypass unit205.

When the input data correspond to one of the enhanced data symbol, thepre-coder bypass unit 205 operates (or calculates) the input data, sothat the pre-coder is bypassed in the trellis encoder 113 in a laterprocess. Then the pre-coder bypass unit 205 outputs the operated (orcalculated) data. When the input data correspond to the main data symbolor the known data symbol, the data are outputted without any change. Theoutput of the pre-coder bypass unit 205 is then inputted to the trellisinitialization controller 208. The operation of the pre-coder bypassunit 205 will be described in detail in a later process.

When the input symbol is the enhanced data symbol, the fourthmultiplexer 207 selects the output bit of the ½-rate encoder 203 insteadof the input bit and outputs the selected output bit. When the inputsymbol is one of the main data symbol and the known data symbol, thefourth multiplexer 207 selects the output bit of the second multiplexer206 and outputs the selected output bit. Then, the selects bits areoutputted to the trellis initialization controller 208.

The trellis initialization controller 208 generates data that enable thememory of the trellis encoder 113 to be initialized to a predeterminedstate, when the sequence of the known data symbol begins. Then, thetrellis initialization controller 208 outputs the generated data insteadof the known data. Furthermore, in the remaining section, the input dataare bypassed without modification. The operation of the trellisinitialization controller 208 will be described in detail in a laterprocess. As a result, the E-VSB symbol processor of FIG. 2A encodes theupper bit X2 among the two input bits of the enhanced data symbol and,then, outputs two bits. Herein, the lower bit X1 is discarded.

FIG. 2B illustrates a block view of an E-VSB symbol processor accordingto another embodiment of the present invention. Herein, FIG. 2A and FIG.2B are very similar to one another. However, the difference between thetwo E-VSB symbol processors is that, in the one shown in FIG. 2B, thelower bit X1 among the two input bits of the enhanced data symbol isencoded, thereby outputting two bits, whereas the upper bit X2 isdiscarded. Referring to FIG. 2B, when the input symbol is one of a maindata symbol M and an enhanced data symbol E, the first multiplexer 251selects an upper bit X2 of a symbol outputted from the byte-symbolconverter 108. Alternatively, when the input symbol is a known dataplace holder symbol (or a known data symbol) T, the first multiplexer251 selects an upper bit X2 of a symbol outputted from the known datagenerator 110. Thereafter, the first multiplexer 251 outputs theselected upper bit X2 to the third multiplexer 252.

Additionally, when the input symbol is one of a main data symbol M andan enhanced data symbol E, the second multiplexer 254 selects a lowerbit X1 of the symbol outputted from the byte-symbol converter 108. And,when the input symbol is a known data symbol T, the second multiplexer254 selects a lower bit X1 of the symbol outputted from the known datagenerator 110. Thereafter, the second multiplexer 254 outputs theselected lower bit X1 to the demultiplexer 255. When the output bit ofthe second multiplexer 254 is the enhanced data, the demultiplexer 255outputs the output bit to the ½-rate encoder 256. Alternatively, whenthe output bit is the main data or the known data, the demultiplexer 255outputs the output bit to the fourth multiplexer 257.

The ½-rate encoder 256 performs ½-rate coding on the enhanced data bitoutputted from the demultiplexer 255, thereby generating 2 bits. Herein,one of the 2 bits is outputted to the third multiplexer 252, and theother bit is outputted to the fourth multiplexer 257. When the inputdata is one of the main data and the known data, the third multiplexer252 selects the output bit of the first multiplexer 251. And, when theinput data is the enhanced data, the third multiplexer 252 selects theoutput bit of the ½-rate encoder 256. Then, the third multiplexer 252outputs the selected bit to the pre-coder bypass unit 253. When theinput data correspond to the enhanced data, the pre-coder bypass unit253 operates (or calculates) the input data, so that the pre-coder isbypassed in the trellis encoder in a later process. Then, the pre-coderbypass unit 253 outputs the operated (or calculated) data. When theinput data correspond to the main data or the known data, the data areoutputted without any change. The output of the pre-coder bypass unit253 is then inputted to the trellis initialization controller 258.

When the input symbol is the enhanced data symbol, the fourthmultiplexer 258 selects and outputs the other output bit of the ½-rateencoder 256. When the input symbol is the main data symbol or the knowndata symbol, the fourth multiplexer 258 selects the output bit of thedemultiplexer 255 and outputs the selected bit to the trellisinitialization controller 258. The trellis initialization controller 258generates data that enable the memory of the trellis encoder 113 to beinitialized to a predetermined state, when the sequence of the knowndata symbol begins. Then, the trellis initialization controller 258outputs the generated data instead of the known data. Furthermore, inthe remaining section, the input data are bypassed without modification.As a result, the E-VSB symbol processor of FIG. 2B encodes the lower bitX1 among the two input bits of the enhanced data symbol and, then,outputs two bits. Herein, the upper bit X2 is discarded.

Meanwhile, the E-VSB pre-processor 101 of FIG. 1 performs pre-processingsteps such as additional error correction encoding, byte expansion, andso on, on the enhanced data. At this point, the processing method of theE-VSB symbol processor may vary in accordance with the byte expansionmethod of the E-VSB pre-processor 101. Examples of the same are shown inFIG. 3A to FIG. 3C and also in FIG. 4A to FIG. 4C. Herein, FIG. 3A toFIG. 3C illustrate examples of expanding one enhanced data byte to twobytes according to the present invention. And, FIG. 4A to FIG. 4Cillustrate examples of expanding one enhanced data byte to four bytesaccording to the present invention. FIG. 3A and FIG. 4A are mosteffective when applied to the E-VSB symbol processor of FIG. 2A.Alternatively, FIG. 3B and FIG. 4B are most effective when applied tothe E-VSB symbol processor of FIG. 2B. FIG. 3C and FIG. 4C may beapplied in any one of FIG. 2A and FIG. 2B. The byte expansion includesthe method of inserting null data bits between each bit and the methodof repeating each bit.

FIG. 3A illustrates an example of the E-VSB pre-processor 101 expandingone enhanced data byte to two bytes when using the E-VSB symbolprocessor shown in FIG. 2A. In the E-VSB symbol processor of FIG. 2A,only the upper bit of the enhanced data symbol is used and the lower bitis discarded. Therefore, as shown in FIG. 3A, the E-VSB pre-processor101 inserts a null data bit x after each bit for one input byte, therebyoutputting two bytes. In a later process, the outputted bytes areconverted to a 2-bit unit symbol by the byte-symbol converter andinputted to the E-VSB symbol processor of FIG. 2A. At this point, theupper bit X2 of the input symbol includes information, and the lower bitX1 is a null data bit. Herein, the lower bit X1 is replaced with theoutput bit of the ½-rate encoder 203 by the fourth multiplexer 207 ofFIG. 2A.

FIG. 3B an example of the E-VSB pre-processor 101 expanding one enhanceddata byte to two bytes when using the E-VSB symbol processor shown inFIG. 2B. In the E-VSB symbol processor of FIG. 2B, only the lower bit ofthe enhanced data symbol is used and the upper bit is discarded.Therefore, as shown in FIG. 3B, the E-VSB pre-processor 101 inserts anull data bit x before each bit for one input byte, thereby outputtingtwo bytes. In a later process, the outputted bytes are converted to a2-bit unit symbol by the byte-symbol converter and inputted to the E-VSBsymbol processor of FIG. 2B. At this point, the upper bit X2 is a nulldata bit, and the lower bit X1 of the input symbol includes information.Herein, the upper bit X2 is replaced with the output bit of the ½-rateencoder 256 by the third multiplexer 252 of FIG. 2B.

FIG. 3C illustrates yet another example of expanding one enhanced databyte to two bytes that can be applied to the E-VSB symbol processor ofboth FIG. 2A and FIG. 2B. The null data bit shown in FIG. 3A and FIG. 3Bmay be given an arbitrary value. Therefore, as shown in FIG. 3C, eachbit for one input byte is repeated one time to be expanded to 2 bytes.This expansion method can be applied to the E-VSB symbol processor ofboth FIG. 2A and FIG. 2B.

FIG. 4A illustrates an example of the E-VSB pre-processor 101 expandingone enhanced data byte to four bytes when using the E-VSB symbolprocessor shown in FIG. 4A. In the E-VSB symbol processor of FIG. 2A,only the upper bit of the enhanced data symbol is used and the lower bitis discarded. Therefore, as shown in FIG. 4A, the E-VSB pre-processor101 repeats each bit for one input byte so as to create 2 bits. Then,the E-VSB pre-processor 101 inserts a null data bit x after each bitincluding the repeated bits, thereby outputting four bytes. Morespecifically, the amount of data in the enhanced data is expanded to 4times its initial size. The outputted bytes are converted to a 2-bitunit symbol by the byte-symbol converter and inputted to the E-VSBsymbol processor of FIG. 2A. At this point, the upper bit X2 of theinput symbol includes information, and the lower bit X1 is a null databit. Herein, the lower bit X1 is replaced with the output bit of the½-rate encoder 203 by the fourth multiplexer 207 of FIG. 2A.

FIG. 4B illustrates an example of the E-VSB pre-processor 101 expandingone enhanced data byte to four bytes when using the E-VSB symbolprocessor shown in FIG. 2B. In the E-VSB symbol processor of FIG. 2B,only the lower bit of the enhanced data symbol is used and the upper bitis discarded. Therefore, as shown in FIG. 4B, the E-VSB pre-processor101 repeats each bit for one input byte so as to create 2 bits. Then,the E-VSB pre-processor 101 inserts a null data bit x before each bitincluding the repeated bits, thereby outputting four bytes. Theoutputted bytes are converted to a 2-bit unit symbol by the byte-symbolconverter and inputted to the E-VSB symbol processor of FIG. 2B. At thispoint, the lower bit X1 of the input symbol includes information, andthe upper bit X2 is a null data bit. Herein, the upper bit X2 isreplaced with the output bit of the ½-rate encoder 256 by the thirdmultiplexer 252 of FIG. 2B.

FIG. 4C illustrates yet another example of expanding one enhanced databyte to four bytes that can be applied to the E-VSB symbol processor ofboth FIG. 2A and FIG. 2B. The null data bit shown in FIG. 4A and FIG. 4Bmay be given an arbitrary value. Therefore, as shown in FIG. 4C, eachbit for one input byte is repeated four times to be expanded to 2 bytes.This expansion method can be applied to the E-VSB symbol processor ofboth FIG. 2A and FIG. 2B. By expanding the data byte as shown in FIG. 4Ato FIG. 4C, each bit is coded with a ½-coding rate twice by the E-VSBsymbol processor, which results in a coding rate of ¼ (hereinafterreferred to as a ¼-coding rate) of the bits.

FIG. 5 illustrates a block view of the pre-coder bypass unit 205 or 253included in the E-VSB symbol processor. Referring to FIG. 5, thepre-coder bypass unit according to the present invention includes amultiplexer 510, a pre-coder 520, and a post-decoder 530. Herein, thepost-decoder 530 performs an inverse process of the pre-coder 520. Themultiplexer 510 selects either an input bit or an output bit of thepre-coder 520 in accordance with the input data symbol type. Then, themultiplexer 510 outputs the selected input bit or output bit to thepost-decoder 530. If the input data is an enhanced data symbol, themultiplexer 510 selects the input bit. Conversely, if the input data isa main data symbol or a known data symbol, the multiplexer 510 selectsthe output bit of the pre-coder 520. Thereafter, the selected bit isoutputted to the post-decoder 530. Accordingly, the post-decoder 530post-decodes and outputs the output of the multiplexer 510.

If a main data symbol or a known data symbol is inputted to thepre-coder bypass unit of FIG. 5, the inputted main data symbol or knowndata symbol sequentially passes through the pre-coder 520 and thepost-decoder 530. Therefore, a value equal to that of the input bit isoutputted. Accordingly, when the main data pass through the pre-coderincluded in the trellis encoder, the main data and/or the known data arepre-coded. Meanwhile, when the enhanced data symbol is inputted, theinput symbol only passes through the post-decoder 530. This indicatesthat when the symbol passes though the pre-coder of the trellis encoder,the enhanced data symbol bypasses the pre-coder.

FIG. 6A illustrates a detailed block view of the trellis encoder 113.Herein, two input bits Z1 and Z2 are coded so as to output three bits C0to C2. The upper bit Z2 of the input bit uses a memory M2 so as to bepre-coded and outputted as C2. Alternatively, the lower bit Z1 of theinput bit uses the memories M0 and M1, so as to be trellis-encoded andoutputted as C0 and C1, respectively. The output C2C1C0 of the trellisencoder 113 is mapped to an 8-level VSB signal and outputted. Morespecifically, the trellis encoder 113 pre-codes the upper bit Z2 of theoutput symbol outputted from the E-VSB symbol processor 109, and outputsthe pre-coded upper bit as C2. Furthermore, the trellis encoder 113trellis-encodes the lower bit Z1 and outputs the trellis-encoded lowerbit as C1 and C0. Therefore, the memory M2 of the trellis encoder 113 isdecided only by Z2, and the memories M1 and M0 are decided only by Z1.

As shown in FIG. 6A, one Z2 is required to initialize the memory M2 ofthe trellis encoder to a specific value, and two Z1 are required toinitialize each of the memories M1 and M0 to a specific value.Therefore, in order to initialize the memories M2, M1, and M0 of thetrellis encoder, at least two input symbols are required. FIG. 6Bdescribes a process of inputting two symbols required for initializingan arbitrary memory state M2M1M0 to ‘000’. For example, when the stateof the memory MM21M0 is equal to ‘111’ (i.e., when M2M1M0=111), in orderto initialize the memory M2M1M0 to ‘000’, the input bits Z2Z1 should beconsecutively inputted as ‘01’ and ‘11’ or as ‘11’ and ‘01’.

The trellis initialization controller of the E-VSB symbol controllerreceives the memory value of the trellis encoder and, then, uses thetable shown in FIG. 6B so as to output the input symbol sequencerequired for the initializing process. If the memory state of thetrellis encoder that is to be initialized is not equal to ‘000’, twosymbol sequences different from the ones shown in FIG. 6B are required.However, since such sequences may be easily deduced, a detaileddescription of such process will be omitted for simplicity.

As described above, the trellis initialization controller generates dataso that a memory may be initialized to a pre-decided state in accordancewith the memory state of the trellis encoder during the first two symbolperiods at the beginning of the known data symbol sequence.Subsequently, the trellis initialization controller outputs the newlygenerated initialization data instead of the input data. Thereafter,during the remaining symbol periods, the input data are outputtedwithout modification. The memory of the trellis encoder is initializedso that the known data may be maintained as the known data even afterbeing trellis-encoded. Evidently, the known data symbol being outputtedfrom the trellis encoder is different from the known data symbol beinginputted to the trellis encoder.

FIG. 7 illustrates a block diagram showing the structure of a digitalbroadcast receiving system that receives data transmitted from thedigital broadcast transmitting system shown in FIG. 1 and thendemodulates and equalizes the received data to recover the data to theinitial data. Referring to FIG. 7, the digital broadcast receiverincludes a tuner 701, a demodulator 702, an equalizer 703, a known datadetector 704, a Viterbi decoder 705, a data deinterleaver 706, a RSdecoder/non-systematic RS parity remover 707, and a derandomizer 708.The digital broadcast receiver further includes a main data packetremover 709, an E-VSB packet deformatter 710, and an E-VSB dataprocessor 711.

More specifically, the tuner 701 tunes the frequency of a particularchannel. Subsequently, the tuner 701 down-converts the tuned channelfrequency and outputs the tuned channel frequency to the demodulator 702and the known data detector 704. The demodulator 702 demodulates thetuned channel frequency so as to perform carrier recovery and timingrecovery, thereby creating a baseband signal. Then, the demodulator 702outputs the created baseband signal to the equalizer 703 and the knowndata detector 704. The equalizer 703 compensates for any channeldistortion included in the demodulated signal. Thereafter, the equalizer703 outputs the processed signal to the Viterbi decoder 705.

At this point, the known data detector 704 detects the known data symbolsequence inserted from the transmitting system from the input/outputdata of the demodulator 702 (i.e., the data prior to demodulation or thedata after demodulation). Then, the known data detector 704 outputs thedetected sequence to the demodulator 702 and the equalizer 703. When thedemodulator 702 uses the known data symbol sequence during the timingrecovery or the carrier recovery, the demodulating performance may beenhanced. Similarly, when the equalizer 703 uses the known data symbolsequence, the equalization performance may be enhanced.

The Viterbi decoder 705 Viterbi-decodes the main symbol and the enhanceddata symbol outputted from the equalizer 703, so as to convert thesymbols into data bytes, thereby outputting the newly converted databytes to the deinterleaver 706. The B-level value decided by the Viterbidecoder 705 is provided to the equalizer 703 so as to enhance theequalizing performance. The deinterleaver 706 performs the inverseoperation of the data interleaver of the transmitting system and, then,outputs the processed data to the RS decoder/non-systematic RS parityremover 707. If the received packet is the main data packet, the RSdecoder/non-systematic RS parity remover 707 RS-decodes the receivedpacket. Alternatively, if the received packet is the enhanced datapacket, the RS decoder/non-systematic RS parity remover 707 removes thenon-systematic RS parity byte from the received packet. Thereafter, theprocessed packet is outputted to the derandomizer 708.

The derandomizer 70B performs an inverse process of the randomizer so asto process the output of the RS decoder/non-systematic RS parity remover707. Subsequently, the derandomizer 708 inserts a MPEG synchronizationdata byte at the beginning of each packet and outputs the processedpacket in 188-byte units. The output of the derandomizer 708 isoutputted to the main MPEG decoder (not shown) and to the main datapacket remover 709 at the same time.

Meanwhile, the main data packet remover 709 removes the 188-byte unitmain data packet from the data outputted from the derandomizer 708 andoutputs the processed data to the E-VSB packet deformatter 710.Subsequently, the E-VSB packet deformatter 710 removes (or discards) the4-byte MPEG header byte and the known data byte that have been insertedby the E-VSB packet formatter of the transmitting system, and alsoremoves the null bit or repetition bit that has been inserted for thebyte expansion from the processed data. Thereafter, the E-VSB packetdeformatter 710 outputs the processed data to the E-VSB data processor711. The E-VSB data processor 711 performs an inverse process of theE-VSB pre-processor 101 of the transmitting system, so as to process thedata outputted from the E-VSB packet deformatter 710. Subsequently, theE-VSB data processor 711 outputs the final output data.

As described above, the digital broadcasting system, method, and datastructure according to the present invention has the followingadvantages. More specifically, the digital broadcasting system, method,and data structure according to the present invention is highlyprotected against (or resistant to) any error that may occur whentransmitting supplemental data through a channel. And, the presentinvention is also highly compatible to the conventional receivingsystem. Moreover, the present invention may also receive thesupplemental data without any error even in channels having severe ghosteffect and noise.

Additionally, by inserting known data in a specific place (or position)of the data domain and transmitting the processed data, the receivingperformance of the digital broadcast (or digital television) receiverliable to a frequent change in channel may be enhanced. The presentinvention is even more effective when applied to mobile and portablereceivers, which are also liable to a frequent change in channel andwhich require protection (or resistance) against intense noise.Furthermore, ½-rate coding is additionally performed on the enhanceddata symbol, which bypasses the pre-coder so as to be outputted. Thus,the problems of noise and ghost effect in the channel may be resolve,thereby enhancing the performance.

Furthermore, by outputting the known data as the lower bit of theenhanced data symbol and trellis-encoding the outputted lower bit, or byoutputting the memory value of the trellis encoder as the upper bit ofthe enhanced data symbol and trellis-encoding the outputted memoryvalue, the slicing performance of the receiver may also be enhanced.Finally, when the input data correspond to the enhanced data packet, bydeciding the parity byte place so that the parity byte is outputted thelatest among the bytes in the domain excluding the MPEG header byte andthe known data byte, in accordance with the output of the datainterleaver, the degree of freedom for deciding the inserting positionof the known data sequence may be increased, thereby enabling a longknown data sequence to be provided consecutively to the receiver.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A digital television (DTV) transmitter for processing broadcast data,the DTV transmitter comprising: a pre-coder for pre-coding enhanced datafor forward error correction (FEC); a data formatter for generatingenhanced data packets including the pre-coded enhanced data; amultiplexer for multiplexing the enhanced data packets with main datapackets including main data; a first Reed-Solomon (RS) encoder forRS-coding the multiplexed main and enhanced data packets, the first RSencoder RS-coding the main data packets with a systematic RS encodingscheme and RS-coding the enhanced data packets with a non-systematic RSencoding scheme, wherein 47th, 48th, 49th, 50th and 51st bytes in atleast one of the RS-coded enhanced data packets are non-systematicparity data; and a data interleaver for interleaving data in theRS-coded main and enhanced data packets; and a trellis encoder fortrellis-encoding the interleaved data, the trellis encoder beinginitialized at a beginning of a known data sequence.
 2. The DTVtransmitter of claim 1, further comprising: a second RS encoder forre-calculating parity data of the enhanced data for backwardcompatibility.
 3. The DTV transmitter of claim 1, wherein the trellisencoder pre-codes a first bit among symbols of the interleaved data, andtrellis-encodes a second bit among the symbols of the interleaved data.4. The DTV transmitter of claim 1, further comprising: a framemultiplexer for inserting segment synchronization symbols and fieldsynchronization symbols in the trellis-encoded data.
 5. A method ofprocessing broadcast data in a digital television (DTV) transmitter, themethod comprising: pre-coding enhanced data for forward error correction(FEC); generating enhanced data packets including the pre-coded enhanceddata; multiplexing the enhanced data packets with main data packetsincluding main data; RS-coding the multiplexed main and enhanced datapackets, wherein the main data packets are RS-coded with a systematic RSencoding scheme and the enhanced data packets are RS-coded with anon-systematic RS encoding scheme, and wherein 47th, 48th, 49th, 50thand 51st bytes in at least one of the RS-coded enhanced data packets arenon-systematic parity data; interleaving data in the RS-coded main andenhanced data packets; and trellis-encoding, by a trellis encoder, theinterleaved data, the trellis encoder being initialized at a beginningof a known data sequence.
 6. The method of claim 5, further comprising:re-calculating parity data of the enhanced data for backwardcompatibility.
 7. The method of claim 5, wherein the trellis encoderpre-codes a first bit among symbols of the interleaved data, andtrellis-encodes a second bit among the symbols of the interleaved data.8. The method of claim 5, further comprising: inserting segmentsynchronization symbols and field synchronization symbols in thetrellis-encoded data in a frame multiplexer.